Bidirectional switches, capable of conducting currents and blocking voltages of both polarities, are wildly used in many applications, such as compact motor drives, aircrafts, AC power supply units, electric propulsion of ships, and electric cars. Conventional high-voltage bidirectional switches are constructed by two Si-based insulated gate bipolar translators (IGBTs) connected in reversed series and two power diodes, as shown in FIG. 1(a). In this configuration, the current flows through two different devices, this will lead to a high on-state voltage drop, making the bidirectional switches lose more power. To reduce the on-state voltage drop of bidirectional switches and improve efficiency, controllable switches with high reverse blocking (RB) capability, such as RB-IGBTs, have been developed in recent years. The controllable switches with high reverse blocking (RB) capability are as shown in FIG. 1 (b). In this new configuration, the current only flows through a single device, and shorter current path will be beneficial for reducing the on-state voltage drop and lowering on-state loss. But the new configuration goes against chip-area utilization, because only one of the two current channels can conduct currents in the bidirectional conducting mode. In order to cut the cost of bidirectional switches or improve the chip-area utilization, a monolithic bidirectional switch with only one channel and two gates is proposed, as shown in FIG. 1(c). The monolithic bidirectional switch has only one conductive channel, two currents of different direction flow through one channel, so the chip-area utilization is improved. The on-state voltage drop is reduced when current flows through only one channel.
Gallium nitride is one of the representatives of the third generation of wide bandgap semiconductors, which is attracting widespread attention. The superior performance of Gallium nitride mainly lies in high critical breakdown electric field (˜3.5×106 V/cm), high electron mobility (˜2000 cm2/V·s.), high concentration of two-dimensional electron gas (2 DEG) (˜1013 cm−2), and high temperature working ability. Forbidden band width of GaN materials is up to 3.4 eV, which is 3 times the forbidden band width of Si materials and 2.5 times the forbidden band width of GaAs materials. Intrinsic carrier concentration of the semiconductor materials increases exponentially with the forbidden band width and temperature. Therefore, up to a certain temperature range, more the semiconductor materials forbidden band width, smaller is the intrinsic carrier concentration. This can make the device to have a very low leakage current. In addition, gallium nitride (GaN) is stable in chemical properties, has high temperature resistance, and corrosion resistance and has inherent advantages in high frequency, high power, and anti-radiation application. The high electron migration rate transistor (HEMT) based on AlGaN/GaN heterojunction (or heterojunction effect transistor HFET, modulation doped field effect transistor MODFET) has been widely used in the semiconductor field. This kind of device has the characteristics of high reverse blocking voltage, low positive on-state resistance, and high working frequency, so it can make the semiconductor devices satisfy the requirements of more powerful, smaller volume and higher frequency.
In recent years, in order to achieve low power efficient bidirectional switch, the researchers proposed GaN HEMT devices with reverse conducting type (RC-MISHEMT), but from the above analysis, the bidirectional switch based on reverse conducting type has large on-state voltage drop and on-state loss. In order to further reduce the bidirectional on-state voltage drop and on-state loss and improve the switching efficiency of the switch, the bidirectional switch device is very necessary. Therefore, the invention proposes the GaN-based bidirectional switch device, the structure of which is shown in FIG. 2. Each insulated gate structure near Schottky-contact controls the band structure of the Schottky-contact to change the working state of the device, realizing the bidirectional switch's ability of bidirectional conducting and blocking. Due to the only presence of Schottky in this invention, no heavy element such as gold is necessary, so the present invention is compatible with traditional CMOS technology.